The research will be designed with unsaturated fatty acid auxotrophs of E. coli and S. cerevisiae to determine the characteristics of acyl chains that facilitate cell growth and function. Comparisons of the effects of different analogs will allow determination of the structural features that influence induction of new enzymes and initiation of cellular division or mitochondrial replication. Particular emphasis will be on identifying selective actions of acyl chains beyond the general additive, non-selective action of the sort ascribed to membrane fluidity. The studies are designed to determine the limits of nutrient acyl chain composition that are compatible with normal cell division and response to intracellular metabolic regulators. The results can then be applied to more complex eukaryotic cell systems and eventually extended to interpret the possible impact of various dietary lipids upon human physiology. BIBLIOGRAPHIC REFERENCES: Positional Specificity of Cyclopropane Ring Formation from cis-Octadecenoic Acid Isomers in Escherichia coli (1976). Ohlrogge, J.B., Gunstone, F.D., Ismail, I.A., and Lands, W.E.M., Biochim. Biophys. Acta, in press. A Shift from Phospholipid to Triglyceride Synthesis When Cell Division is Inhibited by trans-Fatty Acids (1976). Graff, G., and Lands. W.E.M., Biochim. Biophys. Acta, in press.